Effect of humidity and nutrient content on the survival of Staphylococcus aureus on a glass surface

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  • Surfaces contaminated with Staphylococcus aureus can play an important role in its transmission throughout communities and hospitals. Previous research on S. aureus surface survivability has generally used high density inocula (>105 CFU mL-1), which may lead to cryptic growth of the cells, as well as swabbing methods of recovery, which may underestimate cell numbers. To avoid these potential issues, the current work assessed S. aureus survivability on glass microscope slides utilizing low-density inocula and an in situ cultivation procedure. The survivability of S. aureus was studied at three relative humidities (27, 58, and 80 %) in two types of suspension media: tryptic soy broth (1/10 or 1/100 strength), or dilute saline solution (0.23 %). Two to three water-repelling perimeters were made on each slide with paraffin wax (1-cm2), and inoculated with 50 - 150 cells, as verified by separate viable cell counts. Slides were incubated at 25 ˚C at each humidity level for up to 196 hours. At suitable time points, triplicate slides were removed and each inoculated area of these slides was overlain with 150 µl molten Baird Parker Agar of 45 ˚C, prior to incubation at 37 ˚C. Decay rates increased with a decrease in nutrients: -0.02 and -0.05 hr-1 for 1/10 and 1/100 strength TSB, and -0.06 hr-1 for dilute (0.23 %) saline solution. Overall, the results suggest low nutrient availability results in an increase in decay rates for Staphylococcus aureus.

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    Conference/Workshop Poster
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    Attribution-NonCommercial-NoDerivatives 3.0 International